Air springs are used to alleviate two mutually movable parts of the vehicle or to change the height level of a vehicle. Known air springs comprise an air spring bellows made of rubber which is connected to an upper closure element, being generally in form of a plate, and to a rolling piston, in order to form an airtight working room. During compression and rebound, the air spring bellows rolls on the outer surface of the rolling piston and compresses the air enclosed in the working room. Thereby, a suspending and/or damping effect is achieved.
For fastening of the air spring bellows on the rolling piston, it is known to provide the air spring bellows with a one-sided bead portion, which is slid open onto a fastening section of the rolling piston. In order to prevent the air spring bellows from being pulled off the rolling piston various measures are known.
A rolling piston is known from DE 694 07 244 T2, whose fastening section is formed from a rounded shoulder sloping inwardly and downwardly to a horizontal flange, and a bead seat area being perpendicular to the flange, wherein a bead portion of an air spring bellows sealingly bears against the shoulder and the bead seat area. In order to prevent the air spring bellows from being pulled off, a plate with an outer peripheral edge is disposed on the rolling piston, partially covering the bead portion of the air spring bellows to form a bead retention lip.
Further, a fastening section of a rolling piston formed as a conical seat is known from DE 10 2008 055 511 A1, the fastening section being provided with a retaining collar in the upper region to hold a bead portion of an air spring bellows and a recess in the lower region between the conical seat and a shoulder to at least partially receive the bead portion.
A further measure to secure a bead portion from being pulled off the rolling piston is known from WO 2012/019805 A1. For this purpose an annular groove into which a locking ring is clipped after the mounting of the air spring bellows is introduced into a fastening section of a rolling piston. The locking ring prevents slipping of the air spring bellows off the fastening section of the rolling piston.
Further, it is known to provide the rolling piston with a buffer element on a side facing the working room which serves as an end stop for the rolling piston to limit the movement of the rolling piston in axial direction.
An air spring with a rolling piston and a buffer element is apparent from US 2008/0246198 A1, the buffer element being connected to the rolling piston via a radially inward snap-lock connection. For this purpose a radially inwardly projecting first latching nose is provided on an inner side of a fastening section formed on a rolling piston, the first latching nose interacting with a second latching nose disposed on a retainment ring connected to the buffer element.
Further, an air spring is apparent from WO 01/42678 A1 whose rolling piston is provided with a buffer element. Furthermore, the buffer element prevents the bead portion of an air spring bellows from being pulled off the rolling piston by the buffer element partial covering a portion of the bead portion. The buffer element is connected via a snap-lock connection with the rolling piston by forming an indentation in the rolling piston interacting with a spring element formed on a buffer element. The rolling piston is thereby complex and expensive to manufacture.